To clarify, I don't believe the developer went bad within a week. My blacks were still fine and I noticed no real difference in color rendition with the last batch I used. But there was a definite shift in the white border of the prints. The whites had lost their snap compared to prints I made with the freshly mixed chemistry. I seriously doubt it's a contamination issue either, but who knows.
Well, I'll keep fooling with the stuff and see how it goes.
Thanks, everyone, for your thoughts.